//Accepted 
#include <algorithm>
#include <iostream>
#include <string>
#include<sstream>
#include<string.h>
#include <cstdio>
#include <vector>
#include <bitset>
#include <cmath>
#include <queue>
#include<stack>
#include <set>
#include <map>
#include<ctime>

using namespace std;

typedef long long ll;
typedef vector<int> vi;
typedef pair<int,int> pii;
typedef pair<double,double> pdd;
typedef unsigned long long ull;

#define FOR(i,a,b) for (int i(a); i < (b); i++)
#define REP(i,n) FOR(i,0,n)
#define SORT(v) sort((v).begin(),(v).end())
#define UN(v) sort((v).begin(),(v).end()),v.erase(unique(v.begin(),v.end()),v.end())
#define CL(a,b) memset(a,b,sizeof(a))
#define pb push_back

int n, a[100000], i, j;
bool process(){
	
}

int main(){
	//freopen("in.txt","r",stdin);freopen("out.txt","w",stdout);
	scanf("%d", &n);
	REP(i,n)scanf("%d", &a[i]);
	
	if(process())printf("YES");
	else printf("NO");
	
	return 0;
}
